The present invention relates to systems for testing and analyzing performance of exhaust treatment devices such as exhaust particulate filters by, for example, testing and analyzing substrate materials that may be used as filtering media in exhaust particulate filters or other exhaust treatment devices.
With the increasing awareness of environmental consequences of emitting atmospheric pollutants, and the corresponding tightening of atmospheric emission regulations, exhaust treatment devices are growing increasingly necessary. Exhaust treatment devices that reduce the volume of particulate matter and/or other non-desired emissions are well known and widely implemented for certain sources of atmospheric pollutants. Some examples are wet scrubbers and various particulate filters that are typically incorporated into industrial plant exhaust systems. These systems are largely or wholly absent from many commercial or retail buildings and establishments. This trend will likely change, whereby many smaller buildings such as, for example, charcoal grill using restaurants, may eventually be required to incorporate particulate filtration systems or other exhaust treatment devices into their respective exhaust systems.
Yet other technologies, particularly those concerning internal combustion (IC) engines, are or will also be impacted by the increasing awareness of atmospheric emissions ramifications and tightening of regulations governing such emissions. For example, IC engine exhaust after-treatment technology is rapidly evolving in response to such regulations. Eventually most or all on-road vehicles, as well as off-highway vehicles or equipment, standalone IC driven devices, for example, generators, pumps, compressors, and/or others, may require exhaust after-treatment devices to reduce the volume of non-desired emissions.
Numerous regulations have already been proposed and implemented to govern emissions of compression ignition or diesel engines. In response, diesel exhaust after-treatment devices, particularly various wall flow filtration devices such as diesel particulate filters (DPFs), are growing increasingly necessary. Many extensive experimental and computational works have been conducted in the past twenty years on wall flow filtration devices, including studies of full-scale and mini-DPFs (small wall-flow monoliths or wafer disks) to gain a more fundamental understanding of DPF filtration and regeneration performance, as well as wall flow filtration device performance generally.
Full scale studies of wall flow filtration devices, such as DPFs, tend to have at least some limitations. For example, simultaneous or sequential variations in the stages of filtration at different locations within the wall flow filtration devices are difficult to discern and account for. In other words, sequencing the filtration processes and understanding the different portions of wall flow filtration devices, as they transitions between being clean, wall-loaded, or cake-layered with soot or other particulates, at any instant during use is difficult.
Furthermore, specifically regarding DPFs that are configured to thermally regenerate, during a regeneration cycle, thermal gradients tend to be established across different portions of the DPFs. Still regarding thermally regenerating DPF wall flow filtration devices, the sequence of particulate oxidation within the filter during regeneration affects the cake, and wall filled sections of the filter differently. In light of these non-uniform conditions within DPFs, and the differences between cake and wall particulate regeneration, during full-scale analyses, reaching accurate conclusions relating to performance of particular substrate materials used as filtering media within DPFs or other wall flow filtration devices can be rather difficult.
Regarding the mini-DPFs, studies using them have primarily focused on extracting kinetic parameters for modeling the regeneration process, gaining a better understanding of reaction phenomena during the regeneration process, or determining collected soot microstructural properties. Previously, a stand-alone device was developed to simultaneously analyze multiple mini-DPFs using various tests, for example, cold flow tests and filing and regeneration experiments. Substrate material chemical and physical properties were evaluated by comparing results of such mini-DPF studies with those of full-scale DPF experiments that were studied under realistic exhaust conditions.
Despite best efforts, however, such mini-DPF studies and other wall flow filtration device studies lacked precise control and manipulation of critical parameters that tend to vary over time and which materially affect filtration performance of the substrate materials. That is, they do not correctly replicate the actual in-use processes occurring during the filling and regeneration of wall flow filtration devices such as particulate filters. This rendered it difficult to accurately compare performance characteristics of different substrate materials or investigate filtration behavior at different filling stages of the substrate materials.